1. Field of the Invention
The invention relates to a can according to the preamble of claim 1.
Cans having a cylindrical can body running around the can axis, a can base and a closure arrangement arranged at the end opposite the can base are used for holding various products. The tightly closable closure arrangement comprises a closure membrane and an outside lid. The closure membrane closes the can cylinder tightly in an end region and optionally consists of paper and/or plastic (in particular laminated with thin aluminum foil), but preferably of a metal foil, in particular of aluminum, all of which is also referred to below merely as membrane or toil for the sake of simplicity. Optionally, the membrane or foil can be removed in a manner known per se with the aid of tear-off tabs. Outside lids are placed on the can for protecting the fragile foil and for closing the can after removal of the foil, the edge of the outside lid extending over the can edge, at least on the outside but optionally also on the outside and inside.
The collar-like edge of the closure membrane is raised toward the can axis, the terminating surface of the foil being in the interior of the can and the collar-like edge extending from the terminating surface toward the or to the can edge at the end face. The membrane collar is generally cylindrical and is firmly connected, or glued or sealed, to a corresponding cylindrical end region of the inside of the can cylinder. The--preferably flanged--can edge may be overlapped by the membrane collar or may be free. If the collar does not extend over the can edge, this facilitates the mounting and tearing off of the foil.
2. Description of the Background Art
WO 96/31406 discloses cans, in particular tin cans, having a membrane foil and having an inverted lid. The membrane foils described therein are at most 0.2 mm thick and consist, for example, of a 50 .mu.m aluminum foil with 20 .mu.m heat-seal coating on the inside and 10-20 .mu.m lacquer on the outside. Depending on the contents and on any lid used, the can base can if required also be formed with a foil and in particular with an overlapping base.
In general, it is preferable if the membrane foil is coated, at least in the region intended for connection to the inner surface of the can--with a heat-seal coating. In principle, however, the inner surface of the can can also be provided in the region mentioned--like that of combination cans (e.g. laminated with aluminum foil)--with a primer or a heat-sealable coat; otherwise, the tight connection frequently requires the use of special--in particular multicomponent--adhesives or heat-seal coatings. In any case, bare or coated tin cans can also be tightly closed therewith.
CH 467 202 describes a can having a closure membrane which consists of flat material which has the same thickness as the can cylinder and from which only a central part surrounded by a break-out line can be removed.
The problem of the at least partly removable closure membrane is that it must be removable with application of a relatively small force. Consequently, impacts of the contents against the closure membrane can cause the closure membrane to break open or at least to leak in the connection region or in the region of the break-out line. Impacts of the contents against the membrane occur, for example, during transport. If the can lid is directed downwards, the gravitational force of the can contents acts on the membrane in addition to the impacts. Most cans are filled through the still open can base, with inserted membrane and mounted outside lid. The contents entering strike the membrane, the force acting on the membrane depending directly on the density and the feed rate of the contents. With fast filling and/or heavy contents, leaks occur if the cans are overfilled. In the case of cans having easily removable membranes the low pressure which occurs during air transport or during transport in mountainous regions may also lead to detachment of the membrane. Even if the action of force leads only to irreversible deformation, this may be undesirable in particular applications.
Although the inserted lids known per se overcome these problems, they are more material-consumptive owing to the required grip ring and are therefore more expensive than outside lids, so that there is a desire for the latter.